GPS system space part

　　The space part is the general term of the GPS artificial satellite. The average height of the artificial satellite is about 20200km, the running track is an ellipse, and the earth is located on a focus of the ellipse; the operating cycle is about 12 hours. Nearly 30 navigation satellites are distributed on the orbit of about 55 ° at about 55 °, and some are spare satellites. The U.S. military can adjust the number of work satellites through ground control. In the GPS system, the GPS satellite is a known point of dynamic dynamics. All navigation positioning information of the user side is calculated based on the "Star" sent by this dynamic known point. The GPS Star Calendar is actually a series of real -time parameters describing the GPS satellite movement and track. The broadcasting star calendar received by the civil GPS module is the forecast star calendar used by the GPS satellite to directly broadcast to the user through navigation telecommunications. Random code C/A coded star calendar and military P code star calendar.

　　For the entire GPS system, the ground control part is actually the core of the entire system. All GPS satellites for navigation positioning are provided by 5 monitoring stations distributed on the ground. The ground system is responsible for monitoring GPS signals, collecting data, calculating and injection of navigation electrical essays, status diagnosis, orbital correction, etc. It is with the massive data processing of the ground monitoring system that the GPS system is operating accurately.

　　We often say that the GPS positioning module is called the user part. It receives and demodys the satellite broadcast C/A code signal like a "radio", with a frequency of 1575.42MHz. The GPS module does not send a signal and is a passive positioning. Through the pseudo -distance distance between the computing and each satellite, the distance between the receiver is obtained from the two parameters of the receiver. The first positioning module requires at least 4 satellites to participate in calculations. It is called 3D positioning. 3 satellites can achieve 2D positioning, but the accuracy is not good. The GPS module continuously outputs the positioning information and auxiliary information of the NMEA format through the serial communication port for the receiver to select the application.

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